Ceramic and tar bonded brick furnace lining



Aug. 22, 1967 BQUVIER 3,337,206

CERAMIC AND TAR BONDED BRICK FURNACE LININC Filed July 6, 1964 INVENTORGEORG 30L) VIER United States Patent Op 3,337,206 CERAMIC AND TAR BONDEDBRICK FURNACE LINING Georg Bouvier, Leoben, Styria, Austria, assignor toVeitscher Magnesitwerke-Actien-Gesellschaft, Schuhertring, Vienna,Austria, a corporation of Austria Filed July 6, 1964, Ser. No. 380,232Claims priority, application Austria, July 9, 1963, A 5,499/63 4 Claims.(Cl. 266-43) ABSTRACT OF THE DISCLOSURE A working lining formetallurgical vessels consisting of ceramically bonded and tar bondedbasic and neutral refractory shapes. Each lining layer consists of theceramically bonded shapes interspersed with a suificient number of thetar bonded shapes, preferably alternating with each other, for thelatter shapes to take up the thermal expansion of the ceramically bondedshapes.

The invention relates to a lining for metallurgical vessels, inparticular crucibles, converters, rotors, and electrical furnaces, usedfor carrying out metallurgical processes, and in particular for thesmelting of steel. Of principal concern in this case are those processesin which pure oxygen is allowed to act on the melt. A satisfactorylining for such vessels has proved to be of ceramically bonded bricks,such as may be obtained by burning (also called kiln firing) or by asmelting process, which bricks are impregnated after the conclusion ofthe process causing the ceramic bond, with a carbon-containing medium.Impregnation with this carbon-containing medium may be effected eitherby immersion in it, or by treatment under vacuum and/or excess pressure,if necessary at elevated temperature. The purpose of this impregnationprocess is to fill the pores of the fired or smelted shaped element withcarbon, in order to render it more resistant to the attack of slag ormetallic baths. The carbon-containing medium may be hydrocarbons, thedistillation products of coal, crude oil or wood, in particular tar orpitch, or finely-dispersed suspensions of soot or graphite in a suitablecarrier liquid. It is also possible to elfect the deposition of thecarbon by means of the decomposition of a carbon-containing gas in thepores of the brick. The shaped elements, which have been treated withcarbon by one of the above methods, may also be fired under reducingconditions. 1

If a metallurgical vessel is lined with such shaped elements, which mayfor example be fired, tar-impregnated bricks, expansion gaps must beprovided to take up the thermal expansion of the bricks until theoperating temperature is reached. In the case of a cylindrical vessel,it is essential to provide within a ring of bricks, i.e., in the case ofa vertical cylindrical vessel in a horizontal direction, space forexpansion of the order of 1%, depending on the material of which thebricks are composed. This expansion space has hitherto been provided bycombustible inserts, preferably of cardboard of appropriate strength.Such combustible inserts are, however, subject to various disadvantages.It is, for example, not possible with these inserts, which are uniformlystrong over their Whole length, to obtain in the case of the lining ofconvex sectors of wall, especially where the radius of the curved sectoris small, a uniform compensation for the expansion over the whole depthof the wall, thus leading to stresses and to the chipping 01f of layersof brick. The principal disadvantage of combustible expansion insertsis, however, that on the heating of the vessel they are rapidly burntout, leaving behind empty gaps. Although these 3,337,206 Patented Aug.22, 1967 ice empty gaps will in the main be filled in again by thethermal expansion of the bricks during the progressive heating of thelining, it is nonetheless possible for the carboncontaining impregnationagents and their distillates to escape through these gaps into theinterior of the vessel. It is also possible for tar distillates from an,e.g., tarcontaining back-ramming attached behind the wearing lining, topass through the gaps. Any escape of the carbon compounds in question tothe outside of the vessel is prevented by the suitably sealed shell,e.g., steel. casing, of the vessel. I

However, in order that the bricks may retain the slagrepellingproperties, imparted to them by the introduction of the carbon, it isnecessary to block the egress of the carbon-containing compounds and toprevent as far as possible the escape of the components and distillatesof these. Since such escape takes place principally through non-sealedgaps, the formation of such gaps must be prevented in advance.

The formation of gaps is furthermore promoted by the fact that theceramically-bonded, e.g., fired, bricks possess, due to their method ofmanufacture, small surface roughnesses, which prevent the gaps becomingcompletely closed even after the burning away of the expansion insertsand the thermal expansion of the bricks.

In order to avoid these disadvantages, it is proposed according to theinvention to line metallurgical vessels with two types of refractoryshaped elements. The shaped elements are of refractory materials whichare chemically basic or neutral. One type of the shaped elements areceramically bonded elements treated with a carboncontaining medium, andthe other type are unfired and bonded with carbon-containing media.

According to the invention, the lining comprises a plurality of layersof these two types of refractory shaped elements, each lining layerconsisting of the ceramically bonded elements interspersed with asufiicient number of the unfired shaped elements or bricks, which havebeen bonded with tar or some such substance, to take up the expansion ofthe ceramically bonded, e.g. fired, shaped elements and to prevent theformation of undesirable gaps. In view of their relatively loosestructure and their tar content, the tar-bonded shaped elements aresufiiciently pliable and compressible for this purpose; this'can also beobtained by the use of lower production pressures, the selection of asuitable quantity of tar or other like bonding agent and of a refractorymaterial of suitable grain size. r

If the occurrence of gaps is prevented in this way, the only route forthe escape of the volatile-compounds in question into the interior ofthe vessel is via the pores in the bricks. This has the furtheradvantage of causing a deposition of carbon in the pores of the bricksdue to the rise in temperature.

As carbon-containing bonding agents for the unfired shaped elements inquestion, first consideration is given to tar, pitch or bitumen, aloneor in combination, it being possible to add further carbon-containingsubstances, such as graphite or soot, in order to increase the carboncontent. These bonding agents can, moreover, be precracked. Bricks,bonded with tar or the like, for the lining of metallurgical vessels arealready known, but in such cases the whole lining has been produced fromthe same material throughout.

BRIEF DESCRIPTION OF DRAWING In the schematic drawings illustratingembodiments of the invention:

FIG. 1 is a perspective view of a part of a lining in a metallurgicalvessel;

FIG. 2 is a plan view of a part of a ring of bricks in anotherembodiment of the lining;

DETAILED DESCRIPTION If ceramically-bonded shaped elements or bricks 1and tar-bonded shaped elements or bricks 2 of approximately the samesize are used for the lining, they can be arranged in checkerboardformation, as shown in FIG. 1. The shell 3 of the vessel, the permanentlining 4 mostly consisting of fired magnesia bricks and the back-ramming5 consisting of tar-dolomite or tar-magnesia rammingmiX are shown insection.

Expansion may be sufiiciently compensated by a brick bonded with tar orsimilar bonding agent interspersed after a certain number of ceramicallybonded bricks, e.g., after every second, third or fourth brick. In FIG.2 there is shown an embodiment wherein one tar-bonded brick 2 isinterspersed after each three ceramically bonded bricks.

In general, however, it will be useful as far as possible to lay onecompressible tar-bonded shaped element into each gap. It is, however,desirable for the material which determines the degree of wear, i.e.,the material which is present in excess, to be ceramically bonded. Thisis effected by having the unfired shaped elements produced in the formof plates 6, i.e., inserts which are considerably narrower than theceramically-bonded bricks 1, a possible width ratio being, e.g., 1:4. Asshown in FIG. 3, in the case of a vertical cylindrical vessel, theseplates 6 are laid in the vertical gaps between the ceramically-bondedbricks 1. In FIG. 3 there are also indicated the furnace shell 3, thepermanent lining 4 and the back ramming 5.

As shown in FIG. 4 it may also prove of practical advantage to combineone ceramically-bonded brick and one tar-bonded unfired plate 6 into asingle unit 7 for ease of handling, e.g., by adhesive means, thussimplifying and shortening the lining process.

All basic or neutral refractory materials may be used as refractorymaterial both for the ceramically-bonded and for the tar bonded bricksor shaped elements, in particular magnesia or periclase (sinteredmagnesia from natural or from purified magnesite or artificiallymanufactured magnesia, e.g., from sea water), dolomitic magnesia,dolomite, if desired with the addition of chromium ore, clay,magnesium-aluminium-spinel, lime or similar materials. According to therequired use, the magnesia may be selected with a high or low ironcontent. (Instead of the term sintered magnesia there are often used theterms calcined magnesia or dead-burned magnesia) Example The followingmaterials were used for the lining of an LD crucible:

(a) Fired bricks: size x 400 x 94 mm. (wedge bricks); pressed ofsintered magnesia, fired in a continuous-type tunnel kiln at approx.1700 C. and then impregnated with steel-works heavy tar by means ofvacuum treatment at an elevated temperature (approx. C).

(b) Tar-bonded plates: size x 400 x 94 mm., from sintered magnesia,mixed with 4% steel-works heavy tar and 2% hard tar and compressed.These two types of brick were laid alternately.

In a comparative experiment an LD crucible was lined partly with bricksaccording to (a) above together with expansion inserts of cardboard andin another part with the combination of bricks according to (a) andplates according to (b), as shown in FIG. 3. It was shown in this casethat the section, lined in the latter fashion, suffered appreciably lesswear than the section lined with fired bricks according to (a) alone.

What I claim is:

1. A lining for a metallurgical vessel, comprising a plurality of layersof two types of refractory shaped elements, said shaped elements beingof refractory materials selected from the group consisting of chemicallybasic and neutral materials, one of said types of shaped elements beingceramically bonded elements treated with a carbon-containing medium andsubject to thermal expansion at operating temperatures of themetallurgical vessel, and the other type of said shaped elements beingunfired and bonded by a carbon-containing medium, said bonded shapedelements being compressible, and each of said lining layers consistingof said one type of shaped elements interspersed with a sufficientnumber of the shaped elements of the other type for the latter elementsto take up the thermal expansion of the ceramically bonded elements.

2. The lining of claim 1, wherein the bonded shaped elements have theshape of narrow inserts.

3. The lining of claim 2, wherein the ceramically bonded shaped elementsand the narrow inserts are bonded together into single units eachconsisting of a ceramically bonded shaped element and a narrow insert.

4. The lining of claim 1, wherein the two types of shaped elementsalternate with each other in each of said layers, and in adjacent onesof said layers.

References Cited UNITED STATES PATENTS 2,567,007 9/1951 Brassert et al26643 X 3,058,736 10/1962 Martinet 26643 3,190,626 6/1965 Schwabe et al.266-43 X I. SPENCER OVERHOLSER, Primary Examiner.

E. MAR, Assistant Examiner.

1. A LINING FOR A METALLURGICAL VESSEL, COMPRISING A PLURALITY OF LAYERSTO TWO TYPES OF REFRACTORY SHAPED ELEMENTS, SAID SHAPED ELEMENTS BEINGOF REFRACTORY MATERIALS SELECTED FROM THE GROUP CONSISTING OF CHEMICALLYBASIC AND NEUTRAL MATERIALS, ONE OF SAID TYPES OF SHAPED ELEMENTS BEINGCERAMICALLY BONDED ELEMENTS TREATED WITH A CARBON-CONTAINING MEDIUM ANDSUBJECT TO THERMAL EXPANSION AT OPERATING TEMPERATURES OF THEMETALLURGICAL VESSEL, AND THE OTHER TYPE SAID SHAPED ELEMENTS BEINGUNFIRED AND BONDED BY A CORBON-CONTAINING MEDIUM, SAID BONDED SHAPEDELEMENTS BEING COMPRESSIBLE, AND EACH OF SAID LINING LAYERS CONSISTINGOF SAID ONE TYPE OF SHAPED ELEMENTS INTERSPERSED WITH A SUFFICIENTNUMBER OF THE SHAPED ELEMENTS OF THE OTHER TYPE FOR THE LATTER ELEMENTSTO TAKE UP THE THERMAL EXPANSION OF THE CERAMICALLY BONDED ELEMENTS.